1. Field of Invention
The present invention relates to selected anthraquinone colorants and their use in printing inks and toners, particularly phase change inks.
2. Description of Related Art
Many inks and toners have been developed in recent years for use in printing and xerographic processes, and are herein referred to as printing inks and toners. More recently, there has been a strong focus on colored printing inks and toners for creation and/or reproduction of colored images. Such printing inks and toners have specific requirements in terms of both colors and compatibility with the apparatus, substrates and conditions with which they are used. Likewise, the individual components of such printing inks and toners have specific requirements in terms of the same above variables plus compatibility with one another.
Phase change inks in digital printing applications (also sometimes called solid inks or hot melt inks) have in the past decade gained significant consumer acceptance as an alternative to more traditional printing systems such as offset printing, flexography printing, gravure printing, letterpress printing and the like. Phase change inks are especially desirable for the peripheral printing devices associated with computer technology, as well as being suitable for use in other printing technologies such as gravure printing applications as referenced in U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE4205713AL assigned to Siegwerk Farlenfabrik Keller, Dr. Rung and Co.
In general, phase change inks are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the printing media, they quickly solidify to form a predetermined pattern of solidified ink drops.
They are easy to use and safe. They can be easily loaded into the printer by the user, generally in the form of solid sticks of yellow, magenta, cyan and black ink having a solid consistency similar to children""s crayons. Inside the printer, these inks are melted at an elevated temperature in a print head having a number of orifices, through which the melted ink will be ejected onto the desired substrate such as media like paper or an overhead transparency film. Alternatively, the melted ink may be transferred to a rotating drum or the like and then transferred to the substrate. As the ink cools on the substrate, it re-solidifies into the desired image. This resolidification process, or phase change, is substantially instantaneous and a printed, dry image is thus available as the substrate leaves the printer, and is available immediately to the user.
Phase change inks need not contain solvents or diluents that can lead to undesired emissions. In all, the use and specific design of phase change inks address many of the limitations of more traditional ink and printing processes.
Furthermore, because the ink is in a cool, solid form at any time when the user can actually come in contact with the ink, and the ink is in a molten state only inside the printer (inaccessible to the user), it is generally safe to use. These inks also have long-term stability for shipping and long storage times.
Phase change inks generally comprise a phase change ink carrier composition, which is combined with at least one compatible phase change ink colorant. The carrier composition has been generally composed of resins, fatty acid amides and resin derived materials. Also, plasticizers, waxes, antioxidants and the like have been added to carrier compositions. Generally the resins used are water-insoluble and the carrier composition preferably contains no ingredients that are volatile at the jetting temperatures employed. Also, these carrier ingredients are preferably chemically stable so as not to lose their chemical identity over time and/or under elevated temperature conditions.
Preferably, a colored phase change ink will be formed by combining an ink carrier composition with compatible colorant material, preferably subtractive primary colorants. The subtractive primary colored phase change inks comprise four component dyes, namely, cyan, magenta, yellow and black. U.S. Pat. Nos. 4,889,560 and 5,372,852 teach preferred subtractive primary colorants employed. Typically these may comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, C.I. Disperse Dyes, modified C.I. Acid and Direct Dyes, as well as a limited number of C.I. Basic Dyes. Suitable colorants also include appropriate polymeric dyes, such as those described in U.S. Pat. No. 5,621,022 and available from Milliken and Company as Milliken Ink Yellow 869, Milliken Ink Blue 92, Milliken Ink Red 357, Milliken Ink Yellow 1800, Milliken Ink Black 8915-67, uncut Reactant Orange X-38, uncut Reactant Blue X-17, and uncut Reactant Violet X-80, and those described in U.S. Pat. No. 5,231,135.
Colored resin reaction products such as those described in U.S. Pat. No. 5,780,528 issued Jul. 14, 1998, and assigned to the assignee of the present invention, are also suitable colorants.
Polymeric colorants have also been utilized in preparing commercial phase change ink jet inks, as well as potentially for use in other applications, such as gravure printing, and other types of inks and coating applications where coloration is desired. For example, the specific class of polymeric dyes characterized by: (1) an organic chromophore having (2) a polyoxyalkylene substituent and optionally (3) a carboxylic acid or non-reactive derivative thereof covalently bonded to the polyoxyalkylene substituent, have been described in U.S. Pat. No. 5,621,022 (Jaeger et al.).
Anthraquinone dyes and pigments have been employed as chromogens for many applications where colorants are required. Furthermore, it is known to make many derivatives of anthraquinones for specific colorant applications. Yet, anthraquinones and their derivatives have some shortcomings when used in phase change inks. For example, solubility and blooming problems often arise when known anthraquinone dyes are used in phase change inks. They are believed to be caused by the planar nature of the molecules of these colorants. Aggregation of dye moieties can take place more readily when the dye molecules are planar in nature. This aggregation leads to solubility problems at operating temperatures inside printers. Furthermore, unaggregated dye molecules may work their way to the surface of the hardened phase change ink stick, resulting in blooming problems. Furthermore, the manufacturing processes for making commercially available anthraquinone derivative dyes have several disadvantages (e.g., solvents are typically used in making such derivatives, thus requiring solvent recovery, and such processes also involve elaborate purification procedures).
The present invention retains known advantages of anthraquinone chromogens (e.g., wide variety of red to purple to cyan shades, outstanding lightfastness and thermal stability) while overcoming solubility and blooming problems of conventional anthraquinone colorants as well as eliminating manufacturing disadvantages of their preparation.
One aspect of the present invention is directed to solid ink and toner compositions that comprise a colorant that comprises a monofunctional amine-substituted-9,10-anthraquinone compound, optionally with at least one carrier component.
It is a feature of the present invention that this class of anthraquinone dyes can be easily tailored by adjusting the degree of substitution by monofunctional amine substitutents to provide a desirable range of particular color shades.
It is another feature of the present invention that preferred dyes of this class of anthraquinones are liquid at the elevated temperatures at which phase change ink printers and toner fusing apparatus operate, yet are solid at room temperatures.
It is another feature of the present invention that these anthraquinone dyes may be used as either the sole colorant material or can be used with other conventional phase change ink colorant materials in a phase change ink.
It is still another feature of the present invention that these anthraquinone dyes may be employed with conventional phase change carrier components or conventional toner particle carrier components.
It is an advantage of the present invention that this class of anthraquinone dyes is easy to manufacture and form into useful shapes such as ink sticks.
It is an advantage of the present invention that this class of anthraquinone dyes may be made without additional solvents or the need for elaborate purification processes. The amine reactant can act as an initial solvent for the reaction and as the dye reaction product is made, it also can act as a solvent (i.e., it is a liquid at the elevated temperatures at which the reaction is run). This greatly simplifies the manufacture of these dyes.
It is another advantage of the present invention that these anthraquinone dyes do not display typical characteristics of planar molecules because they have sufficiently large substituents condensed thereonto which prevent the anthraquinone molecules from aggregating, as well as compatibilizing the molecules in an ink or toner base, and thus do not have solubility and blooming problems associated with other anthraquinone dyes. Furthermore, these anthraquinone dyes retain desired lightfastness and thermal stability properties for which anthraquinone dyes are known.
The term xe2x80x9c9,10-anthraquinonexe2x80x9d as used herein refers to anthraquinone having the following chemical formula and numbering sequence: 
The 9,10-anthraquinone compounds of the present invention may be substituted by the same or different amines at any available position, such as the 1, 2, 3, 4, 5, 6, 7, and/or 8 position(s). Preferably, the 9,10-anthraquinone is substituted at the 1, 4, 5 and/or 8 position(s). Examples of such compounds include, but are not limited to, the 1-; 1, 4-; 1, 4, 5-; 1, 4, 8-; and 1, 4, 5, 8-substituted-9,10-anthraquinone compounds. In dyes used in the invention, the substituents are preferably monofunctional amines, optionally in combination with oxy-substituents.
Preferred precursor compounds are halo- or oxy-substituted-9,10-anthraquinone compounds. As used herein, the term xe2x80x9coxy-substituted-9,10-anthraquinone compoundxe2x80x9d refers to any 9,10-anthraquinone compound having one or more additional carbonyl groups on one or both of the outer rings, for example, in the positions described above, and tautomers thereof. Halo-substituted-9,10-anthraquinones have halo-substituents such as chloro-substitutents at the corresponding position(s).
The term xe2x80x9csubstituted-9,10-anthraquinone compoundxe2x80x9d as used herein refers to any 9,10-anthraquinone compound or reduced form thereof having one or more substituent groups on one or both of the outer rings, and tautomers thereof. One preferred class of these anthraquinone compounds is the 1,4-oxy-substituted-9,10-anthraquinone compounds (i.e., carbonyl groups are on both of the 1- and 4- positions of one of the outer rings).
Examples of 1,4-oxy-substituted-9,10-anthraquinone compounds include leucoquinizarin and quinizarin. Leucoquinizarin is the reduced form of quinizarin and has the following chemical formula (I): 
Quinizarin has the following chemical formula (II): 
It is particularly preferred to use a mixture of quinizarin and leucoquinizarin. Because quinizarin is less expensive than leucoquinizarin and also is available in a highly purified xe2x80x9csublimedxe2x80x9d form; the preferred molar ratio is in the range of about 1 to about 10 moles of quinizarin per mole of leucoquinizarin.
Suitable monofunctional amines include any monofunctional amine that is capable of being placed on the 9,10-anthraquinone compound, for example by reacting with the oxy-substituted-9,10-anthraquinone compound, to make a suitable colorant or colorants. Preferred monofunctional amines include but are not limited to aliphatic monoamines, aromatic monoamines, aliphatic/aromatic monoamines, fused ring system monoamines, polyoxyalkylenemonoamines, and hydroxyl/amino-containing compounds.
Examples of aliphatic monoamines include any aliphatic primary or secondary amine (e.g., a C1-C22, preferably C12-18 and more preferably C16-18, or higher linear amine, any branched amine or any cyclic aliphatic amine), such as mono- or di-: methyl amine, ethyl amine, (n- and iso)propyl amines, (n-, iso-, and t-) butylamines, (n-, iso-, t-, and the like) pentyl amines, (n-, iso- t-, and the like) hexyl amines, cyclohexyl amines, (n-, iso-, t-, and the like) heptyl amines, (n-, iso-, t-, and the like) octyl amines, (n-, iso-, t, and the like) nonyl amines, (n- and branched) decyl amines, (n- and branched) undecyl amines, (n- and branched) dodecyl amines, (n- and branched) hexadecyl amines, (n- and branched) octadecyl amines, tallow amines, 2,3-dimethyl-1-cyclohexylamine, piperidine, pyrrolidine, and the like. Tallow amines are particularly preferred.
Examples of aromatic monoamines include aniline, anisidine, and the like.
Examples of aliphatic/aromatic amines include aliphatic/aromatic compounds in which the amino group is attached to the aliphatic portion, such as benzyl amine or analogues with longer or additional alkyl chains, and aliphatic/aromatic compounds in which the amino group is attached to the aromatic portion, such as dodecylaniline or analogues with longer, shorter and/or additional alkyl chains.
Examples of fused ring monoamines include rosin amine, dehydroabietyl amine, dihydroabietyl amine, hydroabietyl amine, and the like, such as Amine D(trademark) available commercially from Hercules Inc. of Wilmington, Del.
Examples of hydroxy/amino compounds include ethanol amine or aminopropyldiethylene glycol, commercially available from Dixie Chemical Company of Pasadena, Tex.
Examples of polyoxyalkylenemonoamines include M-series Jeffamines available commercially from Huntsman Chemical Company of Austin, Tex., and the like, such as Rxe2x80x94Oxe2x80x94(CH2xe2x80x94CH(CH3)xe2x80x94O)nxe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94NH2 wherein R is a lower, such as C1-4, alkyl and n is an integer. It should be noted that the condensation product of M-series Jeffamines and the oxy-substituted-9,10-anthraquinone compounds would likely be a viscous liquid at room temperature.
Preferred mono functional amines are aliphatic monoamines, such as octadecyl and tallow amines.
If leucoquinizarin, or a quinizarin/leucoquinizarin mixture, and a monoamine Rxe2x80x94NH2 are reacted together, the reaction products can be illustrated by the following chemical formulae (III) and (IV): 
Similarly, reaction of the following 9,10-anthraquinone compounds with monoamines Rxe2x80x94NH2 under known reducing conditions produces the following reaction products: 
Preferably, these reactions are carried out at temperatures where the amine is in a liquid state (i.e., at or above the melting point of the amine) so that the amine can act as the initial solvent for the reaction and where the reaction product is also a liquid (i.e., at or above the melting point of the reaction product) so that it can act as the solvent as the reaction proceeds toward completion. There is no particular upper limit on the reaction temperature so long as it is a temperature below the degradation point of the reactants and product(s). Preferably, the reaction temperatures are from 60xc2x0 C.-200xc2x0 C., preferably 80-150xc2x0 C., more preferably 90-125xc2x0 C. Too high reaction temperatures should be avoided to prevent degradation of the reaction product or formation of by-products.
This reaction can be carried out in conventional condensation reaction equipment. Preferably, the reaction is conducted under an inert atmosphere at a temperature where a molten reaction mixture is formed until the reaction is complete. The inert atmosphere is used to prevent premature oxidation of any leuco component in the reaction mixture.
The molar ratio of amine reactant to anthraquinone reactant is preferably approximately stoichiometric relative to the desired amine-substituted reaction product(s). The presence of residual amines in the reaction product is not advantageous. Such excess amines tend to be reactive, and can be corrosive to materials with which the dye comes into contact, such as components of a printing machine. In addition, they tend to oxidize and cause discoloration of the ink or toner product. By using stoichiometric amounts of the amines under the conditions described above, these disadvantages are avoided at the same time that the costs of additional amine and the costs and delays of amine and/or solvent removal process steps are avoided.
Thus, for example, with quinizarin and/or leucoquinizarin, the molar ratio of amine reactant to anthraquinone reactant is preferably from about 0.5:1 to about 2:1, such as from about 1:1 to about 2:1. A molar ratio of about 2:1 favors the formation of a cyan colored dye (which is mainly a diamine substituted-9,10 anthraquinone); a molar ratio of 1.5:1 favors a royal blue-colored dye (which is a mixture of monoamine and diamine-substituted-9,10-anthraquinone; a molar ratio of 1:1 favors the formation of a purple-colored dye (which is mainly a monoamine substituted-9,10-anthraquinone).
Colorant compounds of the present invention may be combined with other colorants in making an ink or toner composition. For example, it may be desirable for certain applications to combine the present colorant or colorants with one or more polymeric dyes as described in U.S. Pat. No. 5,621,022 or conventional phase change ink colorants such as those described in U.S. Pat. Nos. 4,889,560 and 5,372,852, which are hereby incorporated by reference in their entirety.
Furthermore, one or more anthraquinone colorants of the present invention (either with or without other colorants present) may be combined with conventional ink or toner particle components, including but not limited to toner resins, charge control agents, flow agents and the like and phase change ink carrier components such as amide waxes (e.g., tetra-amide compounds, hydroxyl-functional tetra-amide compounds, mono-amides, hydroxyl-functional mono-amides), resinous components (e.g., urethane and urea resins, mixed urethane/urea resins), tackifiers, toughening agents, hardeners, adhesion promoters, plasticizers, antioxidants, viscosity reducing agents such as those disclosed in U.S. Pat. Nos. 4,889,560; 4,889,761; 5,372,852; 5,621,022; 5,700,851; 5,750,604; 5,780,528; 5,782,966; 5,783,658; 5,827,918; and 5,830,942, each of which is hereby incorporated by reference in its entirety, and the like.
The preferred amounts of each colorant and its components will depend upon the particular end use application. For example, some colorants of the invention can be used alone in applications such as phase change ink printing, where they have a melting temperature and a viscosity at the jetting temperature that closely parallel those of other phase change inks (e.g., a viscosity of 11-13 cPs at 140xc2x0 C.). This can provide sharp images with a relatively low volume of ink, with various attendant benefits. On the other hand, they can also provide good coloration in amounts of one percent or less by weight with other ink or toner components. Thus amounts such as 0.5-10 wt %, 1-5 wt. % or 1-2 wt. % are desirable for some applications.
Inks and toners of the invention may be used to form images in printing and xerographic processes as described above, and in other ways. For example, inks of the invention may be used as phase change inks in ink jet printing devices, wherein they are melted and droplets of them are ejected directly onto a substrate, or onto an intermediate transfer member such as a drum or belt and then transferred to a substrate. Toner particles of the invention may similarly be electrostatically attracted to an imaging member such as a photoreceptor or the like and transferred directly or through an intermediate transfer member, and fused to the substrate by pressure and/or heat.
The following Examples are presented to illustrate the invention and to be illustrative of the formulations that can successfully be employed, without any intent to limit the invention to the specific materials, processes or structures employed. All parts and percentages are by weight and all temperatures are degrees Celsius unless explicitly stated otherwise.